In general, gas metal arc welding is defined as an arc welding process in which an electrical arc is established between a consumable electrode, such as a wire, and a base metal to be welded. Droplets are formed on the tip of the molten electrode, e.g., wire, and are transferred across the arc. There is an inert or slightly reactive shielding gas that is provided in the arc region to reduce the reaction of the base metal, molten electrode, and the arc that is due to contamination with the atmosphere. A constant voltage/potential power source is utilized to maintain welding voltage invariable at a particular electrode feed speed. The disturbances in the arc region such as shielding gas contamination that can form porosity, weld pool interference, and excessive melt-through can be detected in the current and voltage signals as the power source compensates for these events. Similar types of welding can also include flux core welding and submerged arc welding.
Prior welding strategies measure variations in welding current signals and welding voltage signals in order to track a weld seam, adjust fill volume, or detect shielding gas contamination. In addition, short circuits can be detected as well as pulse frequency in the sampled electrical signals. Another method for detecting weld quality problems is disclosed in U.S. Pat. No. 5,750,957, which issued on May 12, 1998. The method includes determinations based on the standard deviation of the electrical signal, the summed power spectrum of the electrical signal, and/or the average absolute value of the time derivative of the electrical signal and requires a minimum threshold limit.
The present invention is directed to overcoming one or more of the problems set forth above.